It’s been a big month for news on the audiology front. Earlier this month we reported on important discoveries regarding the development of cognitively-controlled hearing aids and the fact that the rate of hearing impairment in teens may be decreasing. Now we have news that scientists have discovered a missing link in inherited hearing loss and may have discovered how the brain determines from where sound is coming.
The missing mutation in hearing loss
Scientists at the National Institutes of Health (NIH)1 have discovered a DNA “fingerprint” that is connected with a type of genetic hearing impairment that affects children. The DNA was found to be connected to a genetic condition called “Enlarged Vestibular Aqueduct” (EVA). The discovery is important because EVA can be an elusive diagnosis. Children with EVA usually pass their newborn hearing tests but begin to slowly lose their hearing in the weeks and months that follow. Hearing can become irregular with episodes of lost hearing followed by periods of recovery.
Now that scientists understand the connection between the DNA and the gene, they can use the information to:
- Better diagnose EVA in children
- Detect whether siblings may develop EVA
- Discover ways to restore gene function that will preserve hearing for those with EVA
EVA affects the tiny channel called the “vestibular aqueduct” that is located between the inner ear and the brain. The channel becomes enlarged in children with the condition, but that doesn’t necessarily cause hearing loss. That is another reason why this discovery is so important; it may help scientists to understand the connection between anatomy and hearing loss.
Where does a sound come from?
The other interesting piece of research from the world of audiology involves the brain and how it determines precisely where a sound is coming from. A study conducted in the UK discovered that while most nerves in the brain detect where a sound is coming from based on where it is located relative to the head, other nerves can detect the actual position of a sound in the external environment.
Previous studies have tested the brain’s ability to judge where a sound is when test participants held their heads in one position. This study looked at whether “head movements change the responses of nerves that track sound location.” 1
The brain identifies sound in two ways:
- Egocentric: Determining where sound is in relation to the head
- Allocentric: Determining where sound is in the environment around us
The study found that the majority of the nerves in the brain track sound by where it is in relationship to the head – egocentric. However, approximately 20% of the brain’s nerves track a sound’s “…actual location in the world, independent of the head”- allocentric.
Authors of the study say the findings could help designers and engineers create better technology for augmented or virtual reality purposes.
1: http://jmg.bmj.com/content/early/2017/08/05/jmedgenet-2017-104721.full (NOTE THIS IS THE CLINICAL JOURNAL)